Sleeve for protecting the peg in the head of a carbon anode electrode and apparatus for producing this sleeve

ABSTRACT

Sleeve-forming apparatus comprising a former of rectangular section around which a strip of sheet aluminum is arranged to be bent to form the sleeve or tube and which has three smooth faces for forming the three flat walls of the tube and a fourth face formed with a V-shaped groove extending parallel to the edges of the former with the base of the groove adjacent to that face of the former over which the wall of the tube which will carry the part of the fourth wall of the tube on which the first flange is formed, a pressure jaw for clamping the aluminum strip against the middle of the three flat faces of the former, a pair of shaping jaws which are arranged to be swung up so that they each closely embrace a different one of the other two flat faces and part of the grooved face of the former in order to bend the strip which is clamped by the clamping jaw against one flat face of the former along the other two flat faces of the former and over the grooved face of the former, and an element having a folding edge which is arranged to be swung against the grooved face of the former so that the folding edge enters the V-shaped groove and forms the first flange and the inclined portion and second flange on the edges of the strip by forcing them into the groove of the former.

United States Patent 1,915,318 6/1933 Hothersall [72] Inventor KarlFricker Meilen, Zurich, Switzerland [21] Appl. No. 786,571 I [22] FiledDec. 24, 1968 Division of Ser. No. 582,117, Sept. 26, 1966 [45] PatentedMay 4, 1971 [73] Assignee Swis Aluminium Ltd.

Chippis, Switzerland [54] SLEEVE FOR PROTECTING THE PEG IN THE HEAD OF ACARBON ANODE ELECTRODE AND APPARATUS FOR PRODUCING THIS SLEEVE 4 Claims,7 Drawing Figs.

[52] US. Cl 72/51, l13/8,113/54 [51] Int. Cl B21d 39/02 [50] FieldofSearch..... 72/51; 113/8, 54, 12 (C), (E), (F), (K); 29/243.57, 243.5,243.52

[56] References Cited UNITED STATES PATENTS 389,828 9/ l 888 Adriance113/8 411,071 9/1889 Solter 113/8 FOREIGN PATENTS 1,210,455 9/1959France ABSTRACT: Sleeve-forming apparatus comprising a former ofrectangular section around which a strip of sheet aluminum is arrangedto be bent to form the sleeve or tube and which has three smooth facesfor forming the three flat walls of the tube and a fourth face formedwith a V-shaped groove extending parallel to the edges of the formerwith the base of the groove adjacent to that face of the former overwhich the wall of the tube which will carry the part of the fourth wallof the tube on which the first flange is formed, a pressure jaw forclamping the aluminum strip against the middle of the three flat facesof the former, a pair of shaping jaws which are arranged to be sw'ung upso that they each closely embrace a different one of the other two flatfaces and part of the grooved face of the former in order to bend thestrip which is clamped by the clamping jaw against one flat face of theformer along the other two flat faces of the former and over the groovedface of the former, and an element having a folding edge which isarranged to be swung against the grooved face of the former so that thefolding edge enters the V-shaped groove and forms the first flange andthe inclined portion and second flange on the edges of the strip byforcing them into the groove of the former.

aluminum mayalso be employed,

CROSS-REFERENCE TO RELATED APPLICATION This application is a division ofmy copending application Ser. No. 582,1 l7,fIled Sept. 26, 1966.

SUMMARY Baked (burnt) carbon anode rod-electrodes or block-elec} trodesfor the fusion electrolysis of aluminum in a fluoride electrolyte aregenerally provided with an iron peg which is inserted in the upper part(the head) of the carbon anode elec-' trode and is fixed there byramming a granular or pasty synthetic carbon composition around it or bypouring in a molten synthetic carbon composition; A carbon anoderodelectrode, for example, ordinarily has a cross section of about300x300 mm. to 500x500 mm. in width and a height of about 400-550 mm.The iron peg is used to connect the'electrode to the power supply byclamping.

When thecarbon anode electrode has been inserted in the electrolyticfumace, its head becomes heated to about 180 C. After 6 days, thetemperature at this point rises on' an average to about 290 C. Becauseof wear, the carbon anode must be gradually lowered. Finally it is solow that the iron peg also dips into the'cryolite melt. The lower end ofthe peg surrounded by the carbon'composition is protected by it, butnotthat part thereof which projects from the carbon electrode. So thatthis part may not scale off and be partly dissolved in the electrolyte,it, also, must be protected. This is achieved, for example, with the aidof a synthetic carbon composition (coke-pitch mixture).which is'rammedor poured into a socket placed in a recess on the head of the anode. ACollar of sheet aluminum (which is hereinafter calledasleeve) is verysuitable as a socket, because aluminum that is melted away does notcontaminate the bathand is recovered in the cathodic layer of aluminum.

For an iron peg with a cross section of 100x100 mm., for example, asleeve which is about l70 l70 mm. in plan and about 100-200 mm. inheight is used. The thickness of the sheet metal, for example, is about1 mm. Hard-rolled pure aluminum sheet, the cleanness and surfacecondition of which (scaly, scratched, etc.) are (practically speaking)of no importance, is advantageously used for making the sleeve. It istherefore advantageous to use waste sheet. Of course, alloyed if it doesnot-contain alloying metals in such quantity as to contaminate thealuminum recovered in the electrolytic cell in an unacceptable manner.

As the iron pegs have a rectangular cross section, preferably one thatis square, sleeves of square or other rectangular cross section areused. To this end, the recess in the head of the carbon anode rod issquare or otherwise rectangular and the sleeve fits closely into thisrecess.

Such a sleeve may consist of a strip of sheet aluminum which is foldedto produce a tube of substantially rectangular cross section with threeflat walls, and with the edges of the strip meeting and interlockingpart way along the fourth wall, one of the edges being bent to form afirst flange projecting inwardly into the rectangle outlining thesleeve,'and the other edge being bent to form an inclined portionextending inwardly into this rectangle and at the end of the inclinedportion an outwardly extending second flange, the first flange hookinginto the outwardly-facing substantially V-shaped groove fonned betweenthe inclined portion and the second flange. With this arrangement nopart of the interlocking edges of the strip lies outside the rectangularsection of the sleeve, and the sleeve can nest easily in a rectangularrecess in the head of a carbon anode electrode around its peg.

With the foregoing and other considerations in view the presentinvention is directed to an improved typeof sleeveforrning apparatus.

2 DESCRIPTION ,OF THE DRAWINGS FIG. 1 shows in horizontal cross sectiona sleeve of a type on which the present sleeve is animprovement;

FIG. 2 shows an improved sleeve, likewise in horizontal cross section; Q

FIG. 3 illustrates diagrammatically and in longitudinal section anapparatus for producing a sleeve such as shown in FIG.

FIGS. 4, 5, and 6 are diagrammatic views from the viewpoint of FIG. 3buton a smaller scale showing three successive working positions of theshaping tool of the apparatus of FIG.

3; and

HO. 7 shows a detail portion of F IG. 6 on an enlarged scale.

' DETAILED DESCRIPTION imately square cross section, but the wallportion 10 with its inwardlyfolded end 11 and the outwardly bend edge 12of the wall portion 13 project from the square plan. The bent edges 11and 12 must still be beaten or pressed flat, so that a clasp joint maybe formed to prevent the sleeve from opening when the synthetic carboncomposition is poured in, and to provide the completely squarehorizontal cross section enabling the sleeve to be inserted in thesquare recess in the head of the anode.

The sleeve for protecting the iron peg according to the presentinvention is likewise made of a strip of sheet aluminum, but is sodesigned that it does not require a clasp joint and tits closely into asquare or other rectangular recess. It is exemplified in FIG. 2, inhorizontal cross section, and has walls 14, 15 and 16 which are'flat andunshaped. A fourth wall 17 consists of a wall portion 18 which is foldedby from the wall 14 and which itself has an edge flange l9 foldedinwardly by, for example, about 90 preferably 90 to or (more generally)by an angle between 45 (more specifically 70) and and a part 20 foldedby 90 from the wall 16 and bent slightly inwards approximately in thelast third of its width and having a flange 21 folded outwards so as tobe at an angle-preferably 90 to 100 between 45 (more specifically 70)and 130 with the plane of wall 17, and preferably substantially paralleltothe flange 19. The flange 21 engages behind the flange 19 in use.Consequently, the wall 17 partially projects inwards, but not outwards.

The width of the part 18 must be at least so large that the flange 21can engage without any difficulty between the wall 1 and the flange 19.On the other hand,'it should be sufficiently I small to support the part20 against yielding to any significant I extent under the pressure ofthe synthetic carbon composition poured in between the iron peg and thesleeve. It is also to be borne in mind that a too narrow wall part 18makes it difficult to produce the sleeve by means ofthe apparatusaccording to the present invention which is described hereinafter. Awidth of 15 to 25 mm. (including rounded corners) is very suitable inthe case of a sleeve with a cross section of about x170 mm. With rigidmaterial, e.g. hard pure sheet aluminum 1 mm. thick, the wall part 18may be up to about 40 mm. wide in the case of the sleeve in questionwithout any disadvantage. The width of the flange 19, including therounded comer, is for example 8 to 10 mm. and that of the flange 21 isabout 10 mm. Small tolerances in the dimensions of the'walls I4, 15 and16 are permissible, since we are not concerned with a high-jprecisionapparatus in the present case.

- The flanges l9 and 21 must be so shaped that they are held together inthe position of use and do not become disengaged from one anotherwithout some external effect. The angle which they each form with theother sheet-metal part must be such that this clamping action is ensuredin the position of use.

After the synthetic carbon composition has been poured in between theiron peg and the present sleeve, there are no more precautions to'betaken with the sleeve.

The supplementary operation of making a clasp joint, necessary with theold FIG. I sleeve, is dispensed with when the sleeve according to thepresent invention is employed, so that expense is saved. In view of thelarge number of carbon electrodes per furnace and the large series offurnaces, this saving of expense is important. Fractions of cents perkg. are counted in the production of aluminum; every fraction saved hasa notable effect in the final balance sheet of a factory.

The present invention contemplates the provision of apparatus forproducing the new sleeve. This apparatus, as exemplified in FIGS. 3 to6, essentially comprises apressureshapingformer 22 with shaping surfaces23, 24, 25 and 26 and shaping edges 27, 28, 29 and 30. It has a recess31 of approximately V-shaped cross section in the surface 23, the recessbeing parallel to the shaping edge 27 and its lowest point being in thevicinity of the edge 27. A pressure jaw 32 can be pressed against thesurface 25 which is opposite the surface 23 with the recess 31. Twobending jaws 33 and 34 can be swung in succession about pivots 35 and36, respectively, and have a free edge offset through 90 with respect toprojections 37 and 38, respectively. These bending jaws are arranged onopposite sides of the press-shaping former 22 with their pivotal axesparallel to the length of the recess 31 and can be swung against thesurfaces 26-and 24,50 that they embrace the edges 27 and 28. The bendingjaw 33, the projection 37 of which is located in the vicinity of therecess 31 during the operation of the apparatus, is arranged to be swungfirst. An element 39 equipped with a sharp folding edge 40 can swingabout a pivot spindle 41 into a position in which its folding edge 40engages in the recess 31. Driving and control means known per se areprovided for actuating the pressure jaw 32, the bending jaws 33 and 34,and the element 39, as well as for ejecting the sleeve.

Of course, the width of the surfaces 23, 24, 25 and 26, the bending jaws33 and 34 and the edge 40 is related to the width of the sheet metal tobe worked, that is the height of the sleeve to be produced.

The apparatus is preferably set up with the former 22 directed upwards,but it could also be used in any other desired position.

In FIGS. 3 to 6 it is assumed that the apparatus is in the preferredposition, with the former 22 directed upwards. The sheet aluminum isunwound from a reel in the form of a strip 42 which, for example, isabout l--200 mm. wide and about 1 mm. thick by means of rolls serving asa conveying device and is introduced into the gap between the former 22and the pressure jaw 32, pushed forward until it is in the vicinity ofthe free end of the bending jaw 33 and cut to the required length. Thesheet metal is indicated in FIGS. 3 to 6 in chaindotted lines. Theformer 22 has on the side where the surface 23 is located, along therecess 31, a marginal surface 43 which preferably slopes slightlydownwards; this slope is provided to take into consideration thespringing back of the folded sheet metal. After ejection, the marginalpart 18 (FIG. 7) should form a right angle with the wall 14. Thesidewall 44 of the recess 31 is at an angle of about 90", preferablysomewhat less (up to about 80), to the marginal surface 43. The sidewall45 of the recess 31 forms in turn an obtuse angle of, for example, 145to 165 with the surface 23 of the former. The groove 46 is advantageous,because it receives small portions of material by which the requiredlength of the piece of sheet metal cut to size is exceeded, but it isnot absolutely essential. The length of the strip 42 emerging betweenthe former 22 and the pressure jaw 32 should be such that the strip canbe bent around the edges 30 and 27 onto the surface 44 (FIG. 3) and formthe flange 19 (FIG. 7) at this point. A limit switch (not shown) isarranged at the point of furthest advance of the sheet-metal strip 42and, on contact with the sheet metal 42, stops the conveying device bytransmitting a pulse. At the same time, the sheet metal is clampedupwardly against the former 22 from below by the pressure jaw 32 and theshears, which are 4 likewise not shown, are operated and cut the sheetmetal from the strip to the required length. That part of the piece ofsheet metal cut to size which projects beyond the bending jaw 34 must beof such length, that, after being bent round the edges 29 and 28, itextends as far as the marginal surface 43, covers at thisv point theother end of the piece of sheet metal cut to size, which end is bentround the edge 27, and can form the flange 21 (FIG. 7) under the effectof the pointed folding member 40.

The bending operation begins simultaneously with the cutting off orimmediately thereafter, by the bending jaw 33 comprising the projection37 bending one part of the'piece of sheet metal cut to size round theedges 30 and 27. The position reached is shown in FIG. 4. As can beseen, the edge 47 of the sheet metal projects horizontally beyond theinner edge 49 of the surface 43 approximately as far as the middle ofthe recess 31. Shortly thereafter, the longer part of the piece of sheetmetal cut to size is bent round the edges 29 and 28 of the former 22 bythe bending jaw 34 comprising the long projection 38, so that after thisoperation has been carried out the two ends of the sheet metal arelocated over the recess 31, as shown in FIG. 5. It is apparent from thisthat after this operation the edge 48 of the sheet metal covers the edge47 to beyond the edge 49.

It is furthermore apparent from FIG. 5 that, the right-angled projection37 of the bending jaw 33 extends only so far over the surface 43 that itdoes not interfere with the placing of the edge 48 on the edge 47 by thebending jaw 34. The projection 38 does not need to be longer than theprojection 37, because its function is to bend the piece of sheet metalcut to size round the edge 28 through 90. In the illustrated example,however, it is considerably longer, so that the sheet metal is guidedover a longer distance after being bent round the edge 28 and its edge48 rests satisfactorily on the edge 471w hen, during the next operation,the sharp edge forces the two edges lying one on the other into therecess 31.

In the position according to FIG. 5, the transmission of. a

7 pulse, for the bending element 39 takes placeby way of a limit switchand the bending element forces the two free ends, 47 and 48 of the cutpiece'of sheet metal into the groove by means of the edge 40, as aresult of which the final position according to FIG. 6is reached. Inthis FlG., the folded flanges 19 and 21 of the sleeve as shown in FIG. 2can be-seen.

The sleeve is now finished. The bending jaws and the element 39 areswung back, the pressure jaw 32 is lowered and the sleeve is ejectedautomatically. I

Of particularly great importance in the apparatus according to thepresent invention are the recess 31 in the former'22 and the pointedfolding member of the element 39, the cooperation of which produces thefolding of the free ends of the cut.

piece of sheet metal in the required manner in a single operation, theflanges 19 and 21 being formed.

When the sleeve ejected from the apparatus according to the presentinvention is employed, it is opened at the flanges Hand 21 and placedround the iron peg of the carbon anode rod, whereupon the flange 21 ismade to engage behind the flange 19 and the sleeve is inserted in thesquare recess in the head of the carbon anode rod.

Iclaim:

1. Apparatus for producing a sleeve for protecting the head of a carbonanode electrode, which sleeve has generally the' same rectangular crosssection throughout its length with;

three flat walls and a fourth wall with narrower and wider sectionsinterconnected by a clasp joint to maintain said sections coplanar inservice, said apparatus comprising a former of generally rectangularcross section presenting a first smooth face with parallel edges, asecond and a third smooth face disposed at right angles to said firstface and a fourth face generally parallel to said first faceinterconnecting said second and third face along edges parallel to saidother edges, a generally V-shaped groove formed in said fourth faceparallel to said edges and relatively close to said second face anddivid ing said fourthface into a relatively narrow section and a rela--tively wide section, 'a pressure jaw for clamping an aluminum strip ofgiven length to said first face, a first and a second shaping jawassociated with said'first and second faces, means for swinging saidfirst jaw to-bend and clamp said aluminum strip I with a portion thereoffirmly against said second face and another portion thereof against thenarrower portion of said fourth face with a marginal portion thereofpartially overlapping said V-shaped groove for a portion of its width,means for swinging said second jaw to bend and clamp said aluminum stripwith a portion thereof firmly against said third face and anotherportion thereof against the wider portion of the fourth face with aportion overlapping said V-shaped groove and overlying the aluminumstrip portion bent against the narrower portion of said fourth face, andmeans including an element having a folding edge movable to cause saidfolding edge to engage the overlying aluminum strip in the vicinity ofthe groove to press the marginal portion of the strip partiallyoverlapping the groove'into facewise engagement with the groove walladjacent the narrower portion of the fourth face to form a first flangeof said partially overlapping portion and to press a portion of theoverlying strip into facewise engagement with the groove wall adjacentthe wider portion of the fourth face and with its marginal portionforming a second flange in facewise engagement with said first flange,said narrower portion of said fourthface being progressively inclinedinwardly from its intersection with' said third face to the adjacentsidewall of saidgroove, and said adjacent sidewall of said groove beinginclined'at between 80 and 90 to said narrower fourth face portion, andthe other wall of said groove forming an obtuse angle with the widerportion of said fourth face, whereby said flanges formed on saidaluminum sleeve when interengaged to form a clasp joint aresubstantially perpendicular to the said fourth wall of said sleeve andthe narrower and wider portions of said fourth wall are substantiallycoplanar.

2. Apparatus according to claim I, in which the obtuse angle is between145 and 165.

3. Apparatus according to claim 1, in which asubsidiary groove is formedat the base of the V-shaped groove to accommodate any excess sheetmaterial during the forming operation.

4. Apparatus according to claim 1, in which the means provided with theelement having the folding edge is pivotally mounted on an axis situatedbeyond the plane of the third face and on the side thereof opposite thegroove to enable move ment of the folding edge into the groove by theswinging movement of said means.

1. Apparatus for producing a sleeve for protecting the head of a carbonanode electrode, which sleeve has generally the same rectangular crosssection throughout its length with three flat walls and a fourth wallwith narrower and wider sections interconnected by a clasp joint tomaintain said sections coplanar in service, said apparatus comprising aformer of generally rectangular cross section presenting a first smoothface with parallel edges, a second and a third smooth face disposed atright angles to said first face and a fourth face generally parallel tosaid first face interconnecting said second and third face along edgesparallel to said other edges, a generally V-shaped groove formed in saidfourth face parallel to said edges and relatively close to said secondface and dividing said fourth face into a relatively narrow section anda relatively wide section, a pressure jaw for clamping an aluminum stripof given length to said first face, a first and a second shaping jawassociated with said first and second faces, means for swinging saidfirst jaw to bend and clamp said aluminum strip with a portion thereoffirmly against said second face and another portion thereof against thenarrower portion of said fourth face with a marginal portion thereofpartially overlapping said V-shaped groove for a portion of its width,means for swinging said second jaw to bend and clamp said aluminum stripwith a portion thereof firmly against said third face and anotherportion thereof against the wider portion of the fourth face with aportion overlapping said V-shaped groove and overlying the aluminumstrip portion bent against the narrower portion of said fourth face, andmeans including an element having a folding edge movable to cause saidfolding edge to engage the overlying aluminum strip in the vicinity ofthe groove to press the marginal portion of the strip partiallyoverlapping the groove into facewise engagement with the groove walladjacent the narrower portion of the fourth face to form a first flangeof said partially overlapping portion and to press a portion of theoverlying strip into facewise engagement with the groove wall adjacentthe wider portion of the fourth face and with its marginal portionforming a second flange in facewise engagement with said first flange,said narrower portion of said fourth face being progressively inclinedinwardly from its intersection with said third face to the adjacentsidewall of said groove, and said adjacent sidewall of said groove beinginclined at between 80* and 90* to said narrower fourth face portion,and the other wall of said groove forming an obtuse angle with the widerportion of said fourth face, whereby said flanges formed on saidaluminum sleeve when interengaged to form a clasp joint aresubstantially perpendicular to the said fourth wall of said sleeve andthe narrower and wider portions of said fourth wall are substantiallycoplanar.
 2. Apparatus according to claim 1, in which the obtuse angleis between 145* and 165*.
 3. Apparatus according to claim 1, in which asubsidiary groove is formed at the base of the V-shaped groove toaccommodate any excess sheet material during the forming operation. 4.Apparatus according to claim 1, in which the means provided with theelement having the folding edge is pivotally mounted on an axis situatedbeyond the plane of the third face and on the side thereof opposite thegroove to enable movement of the folding edge into the groove by theswinging movement of said means.